The invention relates to liquid sealed lock hoppers. In one aspect it relates to a liquid sealed lock hopper for introducing particulate material into a high pressure zone. In another aspect, it relates to a liquid sealed lock hopper system for withdrawing particulate material from a high pressure zone. In yet another aspect, it relates to a liquid sealed lock hopper system for introducing and withdrawing particulate material from a high pressure zone.
Valuable products can be extracted from particulate materials such as minerals, by subjecting the materials to conversion conditions including elevated pressure. For example, valuable hydrocarbon products can be produced from kerogen and/or bitumen containing materials, such as coal, oil and tar sands, oil shale, and petroleum residues by subjecting same to processes such as pyrolysis, flash pyrolysis, retorting, extraction, or supercritical extraction. It is sometimes beneficial or necessary to conduct such processes under conditions of high pressure.
A problem which has faced the industry in conducting such processes is that of charging and withdrawing the particulate material to and from the high pressure zone. Gas sealed lock hoppers have been used to partially overcome the problem, but such devices suffer from drawbacks. One problem encountered in the operation of gas sealed lock hoppers is that they must be repressurized between cycles, and repressurizing vessels with gas in expensive, time consuming, and inefficient. Another problem is that the exhaust lock hoppers bleed gas from the system. Yet another drawback to the utilization of gas sealed lock hoppers systems lies in their valving. The valves must operate in a dusty and abrasive environment, with a consequent short working life. It has thus proved difficult to provide valves for such systems which long provide a reliable gas seal across a pressure difference of over about 300 psig (pounds per square inch, gauge). As many processes are conducted at pressures higher than 300 psig the gas sealed lock hoppers must be provided in series to handle the higher pressure difference. Liquid sealed lock hoppers can avoid these problems. It would be desirable to provide a liquid sealed lock hopper to replace a gas sealed system.
One promising liquid seal lock hopper is disclosed by Huebler et al, U.S. Pat. No. 3,729,105, Apr. 24, 1973. In that system, a volume of liquid equal to the volume of solids withdrawn from the lock hopper is introduced as the solids are withdrawn. The liquid must be pumped into the lock hopper cyclically and against a pressure gradient. It would be desirable to provide a liquid sealed lock hopper in which pumping liquid against a pressure gradient need not be in a cyclic fashion, whereby a lower capacity pump could be employed. It would be even more desirable to provide a liquid sealed lock hopper system which substantially mitigates or eliminates the need for pumps capable of pumping a liquid against a high pressure gradient, hereinafter referred to as high pressure pumps.
Another promising liquid sealed lock hopper system is disclosed by Schora, Jr. et al, U.S. Pat. No. 4,247,240 Jan. 27, 1981. Schora is an improvement over Huebler et al in that the introduction of liquid into the high pressure zone is avoided by passing the mixture of particulate and liquid over a screen, and by recovering the liquid from beneath the screen and recycling it to the lock hopper. The mixture of liquid and particulate is lifted by an auger or a bucket ladder on to the screen. It would be desirable to provide a liquid sealed lock hopper in which the need for lifting the liquid to great heights is reduced or eliminated. It would be further desirable to provide a liquid sealed lock hopper for withdrawing particulate material from a high pressure zone without losing pressure from the zone.